Various imaging medical modalities are known, including radiography, computed tomography, magnetic resonance imaging, optical tomography, nuclear imaging, thermography, ultrasound, low coherence interferometry. Systems have been described for processing a medical image to automatically identify the anatomy, physiology, and view from the medical image. Machine leaning has been described in the medical imaging field, including medical image analysis and computer-aided diagnosis. Medical pattern recognition systems have been described that learn from examples. Classification of features such as cancerous tumors based on pattern recognition in raw and reduced (segmented and derived features) image data has been described. The technology holds great promise and there is a continuing need for further development.
The present application describes imaging systems in terms of the example modality of diffuse optical tomography (DOT) applied to early detection of rheumatoid arthritis although many aspects of the disclosed subject matter are applicable to other imaging modalities and physiological and anatomical and/or physiological features or conditions. DOT has many benefits including lack of ionizing radiation, avoidance of the need for contrast agents, cost, size, and contact-free acquisition.
In previous studies relating to the application of optical tomographic imaging for detecting and characterizing inflammation in rheumatoid arthritis (RA), it has been observed that absorption coefficients μa and the scattering coefficient μs inside and adjacent to the joint cavity are elevated in patients with RA compared to healthy subjects. However, using a single optically derived parameter (for example the smallest or the largest absorption coefficient, min(μa) or max(μa)), for classification, sensitivities (Se) and specificities (Sp) of only 0.71 were achieved. Subsequent studies showed that using a continuous wave (CW) instrument to measure the amplitude of transmitted light intensities and combining optically derived parameters, such as max(μa) and min(μa), sensitivities and specificities can be increased to 0.76 and 0.78, respectively. However, CW systems have difficulties separating absorption and scattering effects, which then limit the achievable sensitivities and specificities.